Štefan played six seasons for the Atlanta Thrashers scoring 177 points. During the 2004–05 NHL lockout, Štefan played for Ilves Tampere in the SM-liiga. In 37 games, Štefan collected a total of 41 points including 28 assists. In the playoffs, Štefan had six assists and a goal in seven games.

Štefan earned significant notoriety when he missed and fell on a breakaway towards an empty net against the Edmonton Oilers on January 4, 2007,[2] which allowed a play to develop where fellow Czech Aleš Hemský scored with two seconds remaining to send the game to overtime. The Edmonton goal tied the game 5-5, but Dallas then won 6-5 in a shootout.

After Štefan's contract expired in 2007, the Dallas Stars chose not to re-sign him. Štefan signed with SC Bern of the Nationalliga A, but he only played three games for them before retiring in October 2007, largely due to a serious hip injury, the latest of several chronic injuries that plagued his career.[3] He is currently a player agent in Laguna Beach, California, and a coach at Orange County Ice Palace.[1]